1. Field of the Invention
This invention relates to a numerical control device for controlling a machine tool, and more particularly, to a multi-system numerical control device for singly controlling a machine tool that performs a plurality of kinds of machining or other operations such as turning, milling and loader control.
2. Description of the Related Art
A preparatory function (G-code) of a machining program used for a numerical control device for controlling a machine tool has typically a great difference in instruction system between a lathe (turning) system and a milling system. Thus, either a following technique (1) or (2) has been applied to a case where a work requiring several machining functions such as turning and milling is machined.
(1) As shown in FIG. 1, turning is performed with a special purpose machine controlled by a numerical control device for turning, and then milling is performed with a special purpose machine controlled by a numerical control device for milling.
(2) As shown in FIG. 2, incorporating program data for turning and program data for milling into a single program, machining is performed with a machine controlled by a composite working machine numerical control device that executes control in such a manner as to switch machining between turning and milling in response to a program instruction.
Alternatively, a multi-system numerical control device having a plurality of program analysis means and execution means is also well known. However, a conventional multi-system numerical control device has not employed any means for selecting a machine control means for each system. Thus, a following technique (3) has been applied to a case where a work requiring several machining functions such as turning and milling is machined.
(3) As shown in FIG. 3, machining is performed with a special purpose machine controlled by a numerical control device having a plurality of turning systems and a special purpose machine controlled by a numerical control device having a plurality of milling systems.
The above conventional technique (1) has been extremely disadvantageous from a viewpoint of cost, because of need for the numerical control device for turning and the numerical control device for milling. In machining that needs turning and milling for a single work, this technique (1) requires much time for set-up operations such as removal and mounting of the work, and thereby presents a problem in degradation of working efficiency.
The above conventional technique (2) enables either of control for turning and control for milling to be executed within a single control device. However, this technique (2) employs a method of performing machining in such a manner as to alternately switch machining between turning and milling in the course of a series of machining processes, and thereby failed to apply turning and milling to a plurality of works simultaneously.
The above conventional technique (3) enables a plurality of works to be machined simultaneously, thanks to use of the multi-system numerical control device. However, the preparatory function (G-code) of a required machining program is different in instruction system between the lathe (turning) system and the milling system, so that it has been still necessary for this technique (3) to prepare a multi-system numerical control device for turning and a multi-system numerical control device for milling in order to perform lathing (turning) and milling simultaneously, like the above technique (1).